This application claims the priority of German patent document 103 37 620.8, filed Aug. 16, 2003, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a motor vehicle with a “pre-safe” system which includes at least one vehicle periphery detection device and a suspension arrangement including a shock absorber.
Modern motor vehicles, which have a high safety standard, comprise active and passive safety devices that enable the driver to control his vehicle better, even in critical situations, and thus possibly avoid a vehicle accident. Such devices also help to lower the severity of the accident in case of a crash.
For this purpose, the so-called pre-crash phase, which designates the time period between recognizing (through appropriate vehicle detection systems) a high accident probability and the actual impact of the vehicle, is of special importance. According to results from real accident analyses, in about two-thirds of all accidents this time period immediately before a crash is sufficiently long to draw conclusions about the subsequent impact, to initiate corresponding measures to lower the severity of the accident, and to condition vehicle restraining systems and passengers with respect to the imminent accident.
Safety systems, which are effective in a preventive sense, even prior to a possible accident, and which utilize the pre-crash phase to expand protection of the passengers by employing additional safety measures and reducing the severity of the accident, are called pre-safe systems.
The essential components of a pre-safe system include a vehicle periphery detection sensor system, various versions of which are known.
For example European patent document EP 0 952 459 A2 discloses an object detecting device for a motor vehicle, which comprises a distance sensor system composed of a plurality of distance sensors. The latter are arranged on the motor vehicle so as to scan its environment. An evaluating unit uses data from the distance sensor system to determine the travel path and speed of an object relative to the motor vehicle. The distance sensors can optionally be selected by the evaluating unit and their range, measurement repetition frequency, resolution or operating mode can be modified. This device can make data for different driver assistance devices available simultaneously or successively, and can be used as a pre-crash sensor system.
German patent document DE 197 29 960 A1 describes a method for detecting impacts, especially for motor vehicles, for the purpose of activating passenger protection devices. At least one pre-crash sensor records variations of the relative speed and/or the relative distance of objects within a defined proximity of the vehicle periphery. If the change in relative speed detected by the pre-crash sensor is above at least one given threshold value and/or the relative distance is below a given threshold value, this situation is identified as a safety-critical condition, and the triggering threshold is reduced.
Another method for impact detection in a motor vehicle is disclosed in German patent document DE 101 00 880 A1, which uses radar sensors as the pre-crash sensors to determine an effective mass of an impact object. The effective mass is compared to predefined threshold values to classify the impact object, and the classification then determines the use of restraining devices.
Another method for triggering restraint means in a motor vehicle in case of an impact and/or a collision is described in German patent document DE 100 65 518 A1. In this known method, the acceleration time characteristic is detected in the form of at least one acceleration signal, from which the speed time characteristic is generated, and restraint apparatus that is adapted to a concrete impact situation is released. With the aid of a pre-crash sensor system the impact speed and time are determined in advance of the impact, and the impact situation is classified based on the impact speed. Based on this information, a release time window is determined within which the time characteristic of the speed is generated, and in parallel the acceleration signal is used to determine a threshold value for the speed, taking into consideration the classification of the impact situation. When this pre-crash sensor system comprises at least two suitably arranged pre-crash sensors, a triangulation method can be used to determine also the offset (ie., the impact location and the impact angle). For pre-crash sensing, in this respect for example radar measurements, infrared measurements or also optical measuring methods can be used.
An example for a pre-crash sensing system comprising an image recording device for optically detecting spaced objects is disclosed in German patent document DE 198 42 827 A1.
An increasing problem for traffic safety is the ever-increasing variation of vehicle types (including differences in vehicle geometry, weight, height and stiffness), which pose risks for passenger injuries during a collision. For example SUVs (Sport Utility Vehicles) and pick-ups are more rigid due to their design; in addition, they are higher and on average also heavier than common small cars or limousines. While the differences in size between the vehicles do not necessarily contribute to a so-called crash incompatibility as long as the weight ratio is roughly the same, the vehicle height, vehicle geometry and vehicle rigidity play a more important role with respect to the risk of injuries.
Known pre-safe systems can contribute only little to reducing the severity of the accident during a collision between vehicles of different types. For example, during a collision between an SUV and a limousine or a sports car, only little rigidity and mass compatibility exists between the vehicles. Particularly critical for the passenger is for example the impact of an SUV (with an elevated cross bar structure) on the side of a limousine or a sports car with a low side structure, so the rigid front structure of the SUV impacts the relatively soft area of a door on the limousine or the sports car and penetrates correspondingly far into the limousine or sports car.
A pre-safe system that permits an adjustment of the geometric position of crash elements of two accident partners is disclosed in German patent document DE 199 23 708 A1. In this known arrangement, a motor vehicle includes a sensor system for detecting an impending impact. In the event of an impending impact the sensor device emits a signal to a control device of the motor vehicle, which then causes a positional displacement of the vehicle body prior to the impact, at least on the impact side, by means of a suspension and shock absorber unit that is arranged between the chassis and the body. To ensure that the impact occurs at a height of the vehicle at which the accident-related deformation of the body is reduced and the passive safety devices of the vehicle unfold the best effect, the body is lifted or lowered on one side (the presumed impact side) prior to the impact. In order to ensure a fast positional displacement of the body in the case of an impending impact, the suspension and shock absorber units of the motor vehicle are equipped with pyrotechnic adjusting devices.
The disadvantage with this solution however is that the one-sided lowering or raising of the body is associated with considerable structure fluctuations, which for example when lifting the vehicle tail upon detection of an imminent rear impact, can cause a “dive” of the vehicle front. During a rear impact, the latter effect can cause the vehicle possibly to slide under the vehicle in front of it and can expose the vehicle passengers to further risks. Beyond that, a tilt motion of the vehicle can be confusing and unpleasant to the passengers. Moreover this system has the further disadvantage that additional actuators (in this case, the pyrotechnic devices) and corresponding control devices must be provided in order to lift or lower the body on the impact side.
One object of the present invention, therefore, is to provide an improved motor vehicle pre-safe system of the type mentioned above, which initiates preventive protective measures in a pre-crash phase, and which better protects the passengers of different types of motor vehicles at risk of a collision in case of an actual crash.
Another object of the invention is to provide such a system which can be implemented with the least amount of additional devices.
These and other objects and advantages are achieved according to the invention, by a motor vehicle, particularly a passenger car, comprising a pre-safe system that contains at least one vehicle periphery detection device and a suspension and shock absorber unit, arranged between a vehicle chassis and a body, which can be activated as a function of the signals that are received by the vehicle periphery detection device and evaluated in a data evaluation device. According to the invention, the data evaluation device of the vehicle periphery detection device is connected to a control device of an active chassis control system that activates the suspension and shock absorber unit. The chassis control system is used to perform a vehicle level adjustment that is roughly equal to a lifting motion and is predefined for the respective impact situation. Such a lifting level adjustment of the vehicle by the active chassis control system in response to a detected collision risk improves the energy absorption during the accident and hence the protection of the parties in the accident. Compared to a one-sided height adjustment of the body, the impact reaction during a level adjustment through the lifting motion does not result in the risk of a considerable dive of the vehicle on the side opposite the impact side, and hence during a rear impact even in the risk of moving beneath the vehicle in front.
In general the level adjustment utilizes a side skirt, a cross bar and a center tunnel of the vehicle more for the dissipation of energy (i.e., the impact energy can be dissipated more specifically via the side skirt/cross bar/tunnel line of force).
In an advantageous embodiment of the invention, during a side collision a bumper of the impact vehicle directly contacts a side skirt of the impacted vehicle, providing a high level of energy absorption with the formation of folds on the side skirt, and considerably reducing the intrusion and penetration risk of a vehicle door.
In addition to minimizing penetration into the vehicle interior, it is an object of the passenger protection system during a side impact to achieve a relatively early interception of the passenger. Thus, the intention is to keep the passenger/vehicle contact speed as low as possible, which in turn equates to an early interception and hence pre-acceleration of the passenger. A pre-safe system pursuant to the invention reduces this contact time considerably, especially for the upper body region. The contact speed in the pelvic region of the passenger remains in a tolerable range.
The pre-safe system according to the invention can beneficially be implemented with existing safety and comfort systems in modern vehicles, since it only requires the establishment of a logical connection to a known vehicle periphery detection system (which uses ultrasound, infrared, radar technology or also image detection), and to an active chassis control system, which is already in some cases incorporated as a standard feature.
The active chassis control system selecting the suspension and shock absorber unit can be a chassis system that is known in practice under the term “Active Body Control” (ABC) system.
This Active Body Control system developed by Mercedes Benz consists essentially of a plunger actuator, which is connected in series with a passive steel spring element as well as a hydraulic shock absorber connected in parallel thereto. (That is, this so-called plunger actuator is essentially arranged in series with a conventional suspension strut of a passenger car.) Selection of the plunger actuator occurs individually for each vehicle wheel by means of a control valve. For energy provision purposes an accumulator system and a hydraulic pump are provided, with which a specific selection of the respective control valve can be performed and the respectively desired plunger actuator or the plunger actuator that is suitably actuated by an electronic system is supplied with hydraulic medium or from which said medium is removed.
In order to achieve a high driving comfort level while simultaneously increasing driving dynamics and safety, this system performs a body motion and position detection of the vehicle by means of vertical, longitudinal and cross acceleration sensors as well as by means of level and plunger path sensors, which serve as information sources of a complex control logic system. Electronic control of the hydraulic system occurs based on established control strategies and maps on the basis of measuring variables that describe the current motion of the vehicle body. Hereby the driver can select between a comfort-oriented map and a sports-oriented map by the push of a button.
The preferred Active Body Control system is a so-called semi-active system since the control range of active intervention is limited to 5 Hz. This way all low-pass body motions in the direction of the vehicle vertical axis, (due especially to road influences), about the vehicle transverse axis (from braking and accelerating, and) about the vehicle longitudinal axis (caused in particular by driving in curves and a non-level road that is different on the left and the right) can be minimized as needed, and can be optimally dampened. Higher-frequency vibrations of the wheels are absorbed and damped in this embodiment with conventional passive elements, such as e.g., steel springs and shock absorbers with constant adjustment. Such a concentration of the active intervention of body-relevant low frequencies lowers the demand on the actuators with respect of the reaction speed.
Of course the invention can also be implemented with variations of this Active Body Control system, as described for example in German patent document DE 101 11 551 A1, or with a fully active chassis control system.
The described pre-crash level adjustment can beneficially be included in the circumstances of a real accident situation, wherein the variation frequency of the development and the course of the accident can be taken into consideration in the activation by the control device 8 of the active chassis control system 9.
Depending on the expected impact situation, the level adjustment of the body occurs in a controlled or non-controlled fashion to a lower position of the body or to a maximum height position of the body, which can be at least 40 mm to 50 mm, preferably 80 mm to 90 mm, above a zero position of the body, in a short response time, which amounts to e.g. 0.2 to 0.4 sec. until the maximum height position is reached.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.